In the prior art and also in the present invention a distinction is made between axes and drives. A technological object (i.e. a software entity) is usually referred to as an axis and an actual physical object (e.g. a motor or a power part) as a drive. Normally, an axis powers a drive. Whereas, on the other hand an axis does not power a drive, such an axis is referred to as a virtual axis.
Control methods of the type mentioned in the introduction are above all used if a synchronization is to be ensured at a number of axes (including the control axis). In such cases the prior art involves constant monitored of whether the tracking errors of the auxiliary axes remain within predetermined tolerance ranges. If they do, the control method (=normal operation) is continued. Whereas, on the other hand, in case of an error, as a result of which one of the auxiliary axes leaves its permissible tolerance range, it is possible to switch to an error mode, in which it is possible to deviate from normal operation if required. A control method can for example be implemented, in which said auxiliary axis now becomes the new control axis. An example of this procedure is to be found in DE-C-195 29 430.